In the packaging industry many factors drive the use of plastic containers and closures for various applications including hot-fill applications. Such factors include the continuing migration of beverage packaging as well as other packaging from glass containers to plastic containers, the increasing use of single-serve sizes and the proliferation of juice drinks, nectars, energy drinks and other nutritious beverages. The hot-fill process is essentially a packaging process employed to extend shelf life of the product. Such packaging systems allow products containing even highly perishable ingredients such as milk to be stored without refrigeration for extended periods. Efficient closures are the first line of defense against microbial contamination that would compromise that product shelf life, however closures have been one of the most difficult aspects of totally plastic packaging to incorporate into filling applications such as hot-fill systems. In current beverage hot-fill processing, vacuum develops in the container as a result of cooling of headspace gases in a hermetically sealed closure/container system. The ensuing pressure differential is often strong enough to cause severe container deformation, which is unacceptable to the consumer. To avoid such deformation most plastic beverage bottles are designed with greater thicknesses and collapsible panel geometries to accommodate the volume changes caused by internal vacuum formation. As a result, these dedicated hot-fill beverage containers are significantly more expensive compared to sterile-fill and other containers due to the increased plastic material required for their fabrication. Also, as closure designs are refined, bottlers have the option of eliminating process steps to make operations more efficient and less costly. Newer hot-fill closure systems that alleviate hot-fill limitations are being designed. For example, the PCT application published as WO 2006/053013 to Trude et al. describes a seal with a physically moveable portion useful for hot-fill and pasteurizable bottles. The moveable portion of the seal moves in response to pressure created in a container during the processes of hot-fill and pasteurization and accommodates changes in pressure within the container and prevents ambient air from passing into the container.
United States Patent Application 2004/0265447 to Raniwala describes a method of hot-filling a plastic bottle wherein the bottle is provided with an air permeable membrane-covered hole used to equalize pressure between the interior of the container and the ambient pressure as the bottle and contents cool, after which a seal is mechanically and independently applied over the membrane-covered hole. However, since the sealing means is not an integral part of the device and requires a mechanical step the method does not readily lend itself to an overall automated and rapid hot-filling process. U.S. Pat. No. 7,143,568 to Van Heerden et al. discloses a method for sealing a container that includes a crushable material that is mechanically deformed to effect a seal. Since, such a method does not provide gas venting of the container it not applicable to the filling applications addressed by the containers of the present invention.
Therefore, a need exists for improved methods and container for hot-fill processes wherein a vented container also have an integral capability to self-seal via non-contact or direct contact means, rendering the container system hermetically sealed at the conclusion of the filling process.
A need also exists for improved sealable, vented retort pouches for packaging a variety of perishable foodstuffs.
A further need exists for sealable, vented containers that are pressurizable with a gas such as nitrogen or carbon dioxide prior to sealing.
A still further need exists for sealable, vented containers having a visual indicator activated by the sealing process, wherein the indicator shows that the container has been sealed.
The devices and methods of the present invention address these and other needs.